When the Admiral contacts Lorca, she mentions that the refinery had a defense fleet that was defeated by Klingons. One of the miners mentions the fleet as well in the distress call.
Then why didn't the Klingons finish the job, if they were there and had already defeated whomever was there? Why would they wait multiple hours for more reinforcements to show up?
There were some Suliban who helped along the way, yes, but they weren't initially supposed to be the "good guys". Silik's behavior exemplified that, and he was one of Archer's main adversaries.

In fairness, I can understand why people would want some descriptor of certain events. Having said that, even if an explanation had been given like, the Klingons had taken the orbital batteries by destroying their power supply or something, someone would invariably have criticised that explanation and then questioned how the federation could have left a strategically important location with such average defenses.
